ROS pub/sub node gotogoal.py

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Hi guys, so I'm kind of new trying to make a new node. I have the turtlebot3 burger and found a code called "gotogoal.py". I want to use this code but have to make some changes since it is designed for the turtle simulator packages, topics, msgs, etc. Can someone please explain to me what do I need to change in the code in order to make it work? CODE:

#!/usr/bin/env python
#!/usr/bin/env python
import rospy
from geometry_msgs.msg import Twist
from turtlesim.msg import Pose
from math import pow, atan2, sqrt


class TurtleBot:

def __init__(self):
    # Creates a node with name 'turtlebot_controller' and make sure it is a
    # unique node (using anonymous=True).
    rospy.init_node('turtlebot_controller', anonymous=True)

    # Publisher which will publish to the topic '/turtle1/cmd_vel'.
    self.velocity_publisher = rospy.Publisher('/turtle1/cmd_vel',
                                              Twist, queue_size=10)

    # A subscriber to the topic '/turtle1/pose'. self.update_pose is called
    # when a message of type Pose is received.
    self.pose_subscriber = rospy.Subscriber('/turtle1/pose',
                                            Pose, self.update_pose)

    self.pose = Pose()
    self.rate = rospy.Rate(10)

def update_pose(self, data):
    """Callback function which is called when a new message of type Pose is
    received by the subscriber."""
    self.pose = data
    self.pose.x = round(self.pose.x, 4)
    self.pose.y = round(self.pose.y, 4)

def euclidean_distance(self, goal_pose):
    """Euclidean distance between current pose and the goal."""
    return sqrt(pow((goal_pose.x - self.pose.x), 2) +
                pow((goal_pose.y - self.pose.y), 2))

def linear_vel(self, goal_pose, constant=1.5):
    """See video: https://www.youtube.com/watch?v=Qh15Nol5htM."""
    return constant * self.euclidean_distance(goal_pose)

def steering_angle(self, goal_pose):
    """See video: https://www.youtube.com/watch?v=Qh15Nol5htM."""
    return atan2(goal_pose.y - self.pose.y, goal_pose.x - self.pose.x)

def angular_vel(self, goal_pose, constant=6):
    """See video: https://www.youtube.com/watch?v=Qh15Nol5htM."""
    return constant * (self.steering_angle(goal_pose) - self.pose.theta)

def move2goal(self):
    """Moves the turtle to the goal."""
    goal_pose = Pose()

    # Get the input from the user.
    goal_pose.x = input("Set your x goal: ")
    goal_pose.y = input("Set your y goal: ")

    # Please, insert a number slightly greater than 0 (e.g. 0.01).
    distance_tolerance = input("Set your tolerance: ")

    vel_msg = Twist()

    while self.euclidean_distance(goal_pose) >= distance_tolerance:

        # Porportional controller.
        # https://en.wikipedia.org/wiki/Proportional_control

        # Linear velocity in the x-axis.
        vel_msg.linear.x = self.linear_vel(goal_pose)
        vel_msg.linear.y = 0
        vel_msg.linear.z = 0

        # Angular velocity in the z-axis.
        vel_msg.angular.x = 0
        vel_msg.angular.y = 0
        vel_msg.angular.z = self.angular_vel(goal_pose)

        # Publishing our vel_msg
        self.velocity_publisher.publish(vel_msg)

        # Publish at the desired rate.
        self.rate.sleep()

    # Stopping our robot after the movement is over.
    vel_msg.linear.x = 0
    vel_msg.angular.z = 0
    self.velocity_publisher.publish(vel_msg)

    # If we press control + C, the node will stop.
    rospy.spin()

if __name__ == '__main__':
try:
    x = TurtleBot()
    x.move2goal()
except rospy.ROSInterruptException:
    pass

I tried to run it once and this error came up:

 $ ~/catkinTFM_ws/src/location_monitor/src$ rosrun location_monitor gotogoal.py 
Set your x goal: 0 ...